here is 2gb of ram that is fairly cheap and is good.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820141227
i'm not 100% on this but i dont think you can mix ddr and ddr2 ram, when a more experienced member reads this they will tell for sure, but when i upgrade ram i always keep the same brand, model, etc so i know it is compatible.